Water exchange 4- EtOH

Cation exchange resin. Conditioned before use by successive washing with water, EtOH and water, and taken through two H -Na -H cycles by successive treatment with M NaOH, water and M HCl then washed with water until neutral. 

Fructose-6-phosphate [643-13-0] M 260.1, [a]o 2.5 (c 3, H2O), pK 5.84. Crystd as the barium salt from water by adding four volumes of EtOH. The barium can be removed by passage through the H" " form of a cation exchange resin and the free acid collected by freeze-drying. 

L-Histidine [71-00-]] M 155.2, m 287°(dec), [a] -39.7" (HjO), -hl3.0" (6M HCI). Likely impurity is arginine. Adsorbed from aqueous soln on to Dowex 50-H+ ion-exchange resin, washed with 1.5M HCI (to remove other amino acids), then eluted with 4M HCI as the dihydrochloride. Histidine is also purified as the dihydrochloride which is finally dissolved in water, the pH adjusted to 7.0, and the free zwitterionic base crystallises out on addition of EtOH. 

Cation exchange resins. Conditioned before use by successive washing with water, EtOH and water, and... 

---